This invention relates to multi-section support rails and more particularly to multi-section support rails used in automotive vehicles.
Multi-section support rails are used in many components of an automobile body structure and chassis frame. The underbody rails are often termed frame rails that generally have a front and rear portion. The front portion usually has two sections. One section is designed to provide crush energy management and the other section is crush resistance. The frame rails employed today are composed of two different cross-sectional configurations. The crush energy management section is larger in area with a thinner wall thickness. This section may have a plurality of dimples or indentations that encourage crush initiation at predetermined locations along the length of the section. The first section includes an end profile that will accept slight overlapping of the second section so that joining of the two sections is possible.
The second section is designed to be stiffer and is usually smaller than the first section for various vehicle package constraints. The second section includes an end profile that will fit within the end profile of the first section. Thus the current multi-section frame rails have some redundant material that is required for the overlapping which permits joining of the two sections. The sections are generally joined by bonding, welding and/or mechanical fasteners. The longitudinal configuration of the two sections is completed prior to the joining operation.
The present invention seeks to overcome the disadvantages of the prior art multi-section support rails. To this end it is an object of the present invention to provide an improved multi-section support rail structure configuration which may be applicable to all regions of a vehicle body structure.
In one aspect of the present invention, a multi-section support rail with two sections is provided. In another aspect of the present invention, a first of the sections is crush compliant and the second of the sections is crush resistant. In another aspect of the present invention, the two sections have substantially identical end mating cross-sectional outlines and wall thickness. In yet another aspect of the present invention, the two sections are in longitudinal alignment while being joined at the mating surface. In still another aspect of the present invention, the crush compliant section has a cross-sectional structure with a centrally disposed transverse web extending substantially for the entire length thereof.
In still another aspect of the present invention, the crush resistant section is pre-bent, after joining, to the desired longitudinal configuration. In yet still another aspect of the present invention, the joined sections are hydroformed to the final configuration. In a further aspect of the present invention, the crush resistant section has indentations formed along the length thereof during hydroforming to provide clearance with adjacent components during vehicle assembly. In a yet further aspect of the present invention, the sections are formed by separate extruding processes prior to joining. In a still further aspect of the present invention, the crush resistant section is extruded with a hollow cross-sectional structure with support flanges extending from the outer surface thereof.